-a- RPI and Video library
you need to give specific info what you have installed
also see
i used a own build see
GLVideo not working on Pi 4 running Processing 3.5.3 .
-b- can you show the code
( like what example you use and where you add the
loadPixels command )
you might see in above snap that i added that line and it works.
-c- you can work ( like me ) from remote on your RPI,
that would need to install VNC viewer on your PC
https://www.realvnc.com/en/connect/download/viewer/ ,
and on RPI enable VNC (server) from setup.
again above picture show that i use that here, and i show the connection info for ref.
-d- BUT
if your question is if you can use a laptop as screen for the RPI
YES
if it is a very expensive / rare laptop what has a HDMI INPUT
all normal laptop only have HDMI OUTPUT so can not be used as a monitor.